This reminds me that there are still too many people that don't understand percentages or probability.

Less than 100% chance is not 100% chance, no matter how close it is to 100%.

50% does not mean that a specific person will succeed 50% of the time, it means that there's always a flat 50% chance of success or failure. You could fail 90% of the time even though you had a 50% chance of success every time, because it's not cumulative, but flat probability for each check.

Most RNG systems are not perfectly random in the strictest sense, but can seem close enough. This game uses one of them.